1. Field of the Invention
The present invention relates to a method for correcting clutch data used for controlling a clutch, and more particularly to a method for correcting learned data for clutch control operation.
2. Description of the Prior Art
In the prior art there has been widely used a clutch control system for controlling the operation of a friction type clutch in which the clutch is coupled with an actuator and the amount of operation of the clutch is controlled by the actuator in accordance with an electric control signal generated by a control unit. The clutch control system of this type is employed in, for example, a vehicle automatic transmission system. In the case where the operation of the clutch is controlled by the use of the clutch control system of this type, precise clutch data corresponding to the relationship between the position of a member for operating the clutch and the amount of operation of the clutch is required to ensure appropriate clutch control operation. However, variation in this relationship arises because of variation in manufacture, and also with the passage of time due to the wear of the clutch disc and the like.
Accordingly, if precise control of the clutch is required, it is necessary to carry out appropriate correction of the clutch data representing the relationship by, for example, a learning operation. In the prior art, for correcting such clutch data, the meet position of the clutch pressure plate, at which the rotation of the input shaft of the transmission starts by the beginning of the transmission of torque through the clutch owing to the meeting between the pressure plate and the associated clutch disk, is determined by a learning operation which is, for example, conducted each time the selector is set to its neutral (N) position, and the clutch data necessary for controlling the clutch is corrected by the use of the resulting learned data to obtain the corrected or up-dated clutch data.
However, since the learned meet position data greatly depends upon the temperature of the clutch disk, the following disadvantage may arise in the conventional method. Namely, in the case of a vehicles system, for example, the learned meet position data which is obtained by the first learning operation carried out after the vehicle has been parked for long time is quite different from that obtained after repeated vehicle drive-offs. If the latter data is used for the correction of the clutch data, the rotation of the input shaft may begin when the clutch pedal is released only slightly. Accordingly, there is a disadvantage in that large slip of the clutch may occur at vehicle drive-off if the clutch data is corrected by the use of the latter learned data.